One-Dimensional Porphyrin-Fullerene (C-60) Assemblies: Role of Central Metal Ion in Enhancing Ambipolar Mobility

One-dimensional (1D) nanostructures of pi-conjugated molecules exhibiting excellent charge carrier mobilities have attracted much interest for use in organic electronic devices. Although it is tedious to form such structures, the availability of highly delocalized electron and hole carriers in these donor (D)-acceptor (A) coassemblies realize ambipolar charge transport. Here we demonstrate the use of a simple solution casting method to create an ambipolar donor-acceptor single-crystalline assembly. 1D assemblies of 5,10,15,20-tetraphenylporphyrins (H2TPP, ZnTPP) and fullerene (C-60) exhibit high ambipolar mobility in the range of 0.8-3.4 cm(2)Vs(-1) for electrons and holes with high ON/OFF ratio and low threshold voltage. A direct experimental proof for the pivotal role of the central Zn2+ in tetraphenyl porphyrin, which enables a strong D-A charge transfer interaction in the cocrystal and thereby induces electron (1.35 cm(2)Vs(-1)), hole (3.42 cm(2)Vs(-1)) mobilities, the highest reported for two component D-A assemblies using solution casting, is demonstrated.